Re-gap the spark electrode

Set the spark gap to 5 mm

The help centre: no spark is "normally" caused by the tip being knocked out of place.

1. Close the cylinder valve and let the burner go cold.
2. Twist the burner off the oven.
3. Find the hooked steel tip on the white ceramic insulator beside the burner head.
4. Bend the tip gently with pliers until it sits about 5 mm from the burner head (help centre).
5. With the gas still off, push and turn the dial to check it sparks to the head.
6. Refit the burner and light it as usual.